RPT-NASA's newest planet-hunting spacecraft set for launch in Florida

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By Joey Roulette

CAPE CANAVERAL, Fla., April 16 (Reuters) - A new NASA satellite designed to detect more Earth-like worlds around stars beyond our solar system is due for launch aboard a SpaceX rocket from Florida on Monday, on a quest to expand the known inventory of so-called exoplanets that might harbor life.

The Transit Exoplanet Survey Satellite, or TESS, was set to lift off from Cape Canaveral Air Force Station at 6:32 p.m. EDT, starting the clock on a two-year, $337 million mission in one of astronomy’s newest fields of exploration.

TESS is designed to build on the work of its predecessor, the Kepler space telescope, which discovered the bulk of some 3,700 exoplanets documented by astronomers during the past 20 years and is about to run out of fuel.

NASA expects to pinpoint thousands more previously unknown worlds, perhaps hundreds of them Earth-sized or “super-Earth”-sized — no larger than twice as big as our home planet.

Those are believed the most likely to feature rocky surfaces or oceans, and are thus considered the best candidates for life to evolve, as opposed to gas giants like Jupiter or Neptune.

Astronomers said they hope TESS will help catalog about 100 more rocky exoplanets for further study.

Roughly the size of a refrigerator with solar-panel wings and equipped with four special cameras, TESS will take about 60 days to reach a highly elliptical, first-of-a-kind orbit looping it between Earth and the moon every two and a half weeks.

Like Kepler, TESS will use a detection method called transit photometry, which looks for periodic, repetitive dips in the visible light from stars caused by planets passing, or transiting, in front of them.

But unlike Kepler, which fixed its gaze on a range of stars within a tiny fraction of the sky, TESS will scan a broader swath of the heavens to focus on 200,000 pre-selected stars that are closer and thus among the brightest as seen from Earth.

That makes them better suited for sensitive follow-up analysis for the exoplanet candidates TESS locates.

The TESS survey will concentrate on stars called red dwarfs, smaller, cooler and longer-lived than our sun. Red dwarfs also have a high propensity for Earth-sized, presumably rocky planets, making them potentially fertile ground for closer examination.

And because the planets circling them are bigger relative to the size of the star, and orbit at a closer distance, the slight disruptions of visible light from their transits are more pronounced, scientists said.

Measuring blips in starlight can determine the exoplanet’s size and orbital path. Further observations from ground telescopes can supply its mass and ultimately the planet’s density and composition — whether largely solid, liquid or gas.

TESS itself will not detect life beyond Earth. But its most promising discoveries will undergo closer scrutiny by a future generation of larger, more powerful telescopes that will search for telltale signs of water and atmospheric gases that on Earth are indicators of life. (Reporting by Joey Roulette from Cape Canaveral, Fla.; Additional reporting and writing by Steve Gorman in Los Angeles; editing by Richard Pullin)